Coaxial cable connectors

ABSTRACT

A coaxial cable connector of the type wherein one connector is suitable for a group of cables having the same nominal size and impedance characteristics. Clamping force is applied on the outer conductor of the cable in the radially inward direction upon fastening the backshell to the body of the connector. A subassembly captivated within the backshell forces a deformable material into sealing contact with the outer surface of the cable upon fastening the backshell to the body.

United States Patent [191 Stokes Oct. 7, 1975 COAXIAL CABLE CONNECTORS[75] Inventor: Danny Burton Stokes, Las Vegas,

Nev.

21 Appl. No.: 398,363

[52] US Cl. 339/177 R; 174/88 C [51] Int. Cl. H01R 17/04 [58] Field ofSearch 339/177; 174/75 C, 88 C, 174/89; 339/60 C, 88 C, 89 C, 99 C, 91P, 94 C [56] References Cited UNITED STATES PATENTS 3,107,135 10/1963Keil 339/177 R 3,184,706 5/1965 Atkins 339/177 R 3,526,871 9/1970 Hobart339/177 E 3,678,446 7/1972 Siebelist... 339/177 E 3,686,623 8/1972Nijman 339/177 E 3,740,453 6/1973 Callaghan et a1. 339/177 R X 3,744,0117/1973 Blanchenot 339/177 R 3,761,870 9/1973 Drezin et a1. 339/177 RFOREIGN PATENTS OR APPLICATIONS 679,410 9/1952 United Kingdom 339/177 R861,652 2/1961 United Kingdom...., 339/177 R 1,242,731 6/1967 Germany339/177 R 1,237,468 6/1960 France 174/89 1,065,499 9/1959 Germany 174/89Primary ExaminerRoy D. Frazier Assistant Examiner-Lawrence .1. StaabAttorney, Agent, or FirmDean E. Carlson; John A. Koch [5 7] ABSTRACT Acoaxial cable connector of the type wherein one connector is suitablefor a group of cables having the same nominal size and impedancecharacteristics. Clamping force is applied on the outer conductor of thecable in the radially inward direction upon fastening the backshell tothe body of the connector. A subassembly captivated within the backshellforces a deformable material into sealing contact with the outer surfaceof the cable upon fastening the backshell to the body.

1 Claim, 3 Drawing Figures U.S. Patent Oct. 7,1975 3,910,673

l2 I8 40 42 I6 26 24 38 FIG. 3

COAXIAL CABLE CONNECTORS BACKGROUND OF THE INVENTION The inventiondescribed herein was made in the course of or under Contract AT(26-l)-473 with the US. Atomic Energy Commission.

This invention relates to connectors for coaxial cables of the RF (radiofrequency) type and, more particularly, high-power, low-loss cableshaving foam dielectric and components of relatively large size.

The use of coaxial cables in the transmission of intelligence via thepropagation of electromagnetic energy is well known. It is also wellknown that the intelligence transmitting link must be free fromimpedance discontinuities if distortion of the intelligence is to beavoided. Accordingly, the designer of connectors for coaxial cables forthis type of service must work within very severe constraints.

US. Pat. No. 3,678,446 to Hilbert R. Siebelist, assignor to the US.Atomic Energy Commission, assignee of the present application, describedin some detail the difficulties the large user of coaxial cablesexperienced with regard to providing satisfactory connectors for themultitude of coaxial cables available in any particular nominal size andimpedance rating. To briefly summarize the situation described morefully in the Siebelist patent, prior to the Siebelist invention,generally speaking, each cable of a group of cables having the sameimpedance rating and nominal size had its own connector usuallymanufactured and sold by the manufacturer of the cable which had abackshell design that made it suitable for use with that particularcable and essentially none other. The Siebelist connector overcame thesedifficulties by a particular combination of backshell, body and outerconductor clamping arrangement which was applicable to an entire groupof cables of nominal size and impedance rating even though aconsiderable variance was present within that group of cables withrespect to the configuration, dimensions. etc. of their individualcomponents.

The present invention is directed to solution of the same problems towhich the Siebelist connector was dirccted. However, l have found acombination of components in a cable connector backshell and cable outerconductor clamping arrangement which provides certain importantadvantages over the Siebelist connector.

The connector in accordance with the present invention does not requirethat the outer conductor of a cable be flared in preparation toassembling the connector onto the cable as does the Siebelist connector.Flaring the outer conductor required a number of hand operations byworkmen in the field including the compression of the-end of the outerconductor in a specially designed hand operated die set in order toobtain the appropriate flare angle. Moreover, my connector involves alesser number of loose parts with which the workman in the field mustcontend and requires fewer steps and utilization of fewer specializedtools in connection with its installation. Accordingly, the connector inaccordance with the present invention facilitates and simplifies theconnection of cables in the field while retaining the advantages of theSiebelist connector.

SUMMARY OF THE INVENTION Accordingly, it is an object of this inventionto provide a cable connector of the type which permits one connector tobe suitable for use on a group of coaxial cables which have the sameimpedance characteristics and the same or similar nominal size but havedifferent structural details. It is a further object of the invention toprovide a connector of this general type which is more easily connectedto cables in the field than the connectors previously known.

Briefly summarized, this and additional objects and advantages of theinvention are accomplished by a connector having a backshell whichadmits a number of cables of the same nominal size and employs aradially compressible collet, the configuration of the radially inwardsurface of which grips the outer conductor of the cable. Means areprovided which compress the collet, thereby clamping it onto the outerconductor, upon longitudiinal movement of the backshell with respect tothe body of the connector. An environmental seal is forced intoengagement with the outer surface of the cable in response to the samelongitudinal movement of the backshell that actuates the collet.

The means for compressing the collet include a collet clamp and alongitudinally extending spacer positioned within the backshell. Theradially outer perimeter of the collet and the radially inward perimeterof the collet clamp have complementary surfaces which expand radiallyoutwardly in the forward direction. The forward end of the spacerengages the collet clamp. A deformable material is positioned betweenthe rear end of the spacer and the rear end of the backshell.Accordingly, relative longitudinal movement between the backshell andthe body of the connector upon fastening the two together causes thecollet clamp to be forced forward thereby applying a radially inwardforce to the collet which clamps the collet onto the cable outerconductor. Simultaneously, the deformable material is carried forward bythe rear end of the backshell into forceable contact with the rear endof the spacer. The deformable material is thereby forced to expand inthe radially inward direction into contact with the outer surface of thecable to provide a seal.

Captivation of the spacer and environmental seal within the backshellreduces the number of loose parts with which the workman in the fieldmust contend. Since the interface between the collet and collet clampcan be standardized for the entire group of cables for which theconnector is applicable, the collet is the only component of theconnector that needs to be specialized for particular cables of thegroup.

Additional objects and advantages and a better understanding of theinvention will be apparent after consideration of the followingdescription of preferred embodiments thereof.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 of the drawing is a longitudinalview. primarily in cross-section, of a preferred embodiment of theinvention,

FIG. 2 is a longitudinal view of another connector according to theinvention partially in section to illustrate an alternative to FIG. 1with respect to the collet and dielectric arrangement, and

FIG. 3 shows the backshell subcombination of FIG.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to FIG. 1 of thedrawing, the components of cable connector 10 are shown in the positionsthey assume when connection with cable 12 has been accomplished. Cable12 is a typical coaxial cable having a central inner conductor 14,concentric outer conductor 16, dielectric material 18 between the twoconductors and an outer protective covering 22.

The forward portion of connector also has an outer conductor, innerconductor and mass of dielectric therebetween. While the invention isnot limited to connectors having any particular arrangement orconfiguration of parts in their forward portions, a typical arrangementis illustrated in FIG. 1. The outer conductor takes the form of body 24which may or may not be fabricated from two components as shown in thedrawing. Rearward portion 26 of connector inner conductor 28accommodates entry therein of inner conductor 14 of the cable andforward portion 32 the entry of the inner conductor 33 of a standardinterface 34. Forward end 35 of connector dielectric 36 is of aconfiguration to receive the complementary configuration of dielectricof standard interface 34 in any usual manner which provides thenecessary voltage withstand. Nut 38 is utilized to fasten connector 10to another connection device, which may or may not be identical toconnector 10, in the usual manner.

The manner in which cable 12 is clamped within connector 10 to providethe required mechanical strength of the union and the transition of theouter conductor from the cable to the outer conductor (body 24) of theconnector will now be described. As will be noted in FIG. 1, thepreparation of outer conductor 16 and dielectric 18 of the cablerequires only that they be cut flush and the annulus 40 be cut out ofthe dielectric by a hand tool to accommodate tubular extension 42 of thedielectric 36 to provide satisfactory voltage withstand. Furtherpreparation is unnecessary since securing cable 12 to the connector iseffected through the application of a radial force on outer conductor16. This is accomplished through the combined action of slotted collet44, collet clamp 46 and backshell 52 in the following manner.

The complementary outer surface 54 of slotted collet 44 and innersurface 56 of collet clamp 46 are frustoconical and expandradiallyoutwardly in the forward direction. Accordingly, relativemovement of clamp 46 in the forward direction exerts a radially inwardforce upon slotted collet 44 which causes the collet to be compressedinwardly upon the cable. The forward movement of clamp 46 is broughtabout in conjunction with the relative forward longitudinal movement ofbackshell 52 with respect to body 24 which accompanies the fastening ofthe backshell to the body through suitable means such as complementaryscrew threads 58. The forward thrust on clamp 46 is initially impartedthrough spacer 60 successively from seal 62, washer 64 and rear end 66of the backshell. However, that final forward thrust on clamp 46 whichlocks collet 44 onto outer conductor 16 is applied to the clamp throughradially inwardly extending, forward facing shoulder 68 of backshell 52.

Seal 62, made from a deformable material such as rubber, spacer 60,washer 64 and end 66 cooperate to seal the connection from theenvironment in those applications where an environmental seal isnecessary or desirable. The forceable engagement of the seal betweenspacer 60 and washer 64 causes it to expand radially inwardly intosealing contact with outer covering 22 of the cable. Washer 64 providesa metal to metal contact with end 66 to facilitate the rotation ofbackshell 52 in connection with securing the backshell to the body suchas through screw threads 58. The dimensions of backshell 52, spacer 60,washer 64 and seal 62 are selected to insure that sealing contactbetween the seal and outer covering 22 is effected with that cable ofthe group of cables with which one connector configuration will be usedwhich has the smallest OD. The inner diameter of spacer is sufficientlylarge to accommodate the deformation of excess seal material into theannular space between the spacer and outer covering 22 when connector 10is utilized with cables of larger O.D.

FIG. 2 illustrates an alternative arrangement for providing a voltagewithstand that provides advantages in making connections of certaintypes of cables. It is normal practice when making a connection betweencoaxial components to provide a protrusion of the dielectric of onecomponent into the dielectric of the other component. This increases theair gap spark path between inner and outer conductors to provide asatisfactory voltage withstand. Foamed polyolefin is quite often thedielectric used in coaxial cables whereas polytetrafluoroethylene (TFE)is commonly used in connectors. Since the dielectric constant of TFE issignificantly higher than that of the foamed polyolefin, there will beinstances when the change in impedance caused by the arrangement of FIG.1 will be unacceptable as, for instance, when the dielectric of a cableis sufficiently thin that the thinnest practicable protrusion from theconnector dielectric too greatly affects the actual dielectric value ofthe combination.

Accordingly, the embodiment of FIG. 2 provides an arrangement by whichthe adjustment of the dielectric value can be readily accomplished forparticular cables. As shown, outer cable conductor 16 and an outerportion of the cable dielectric 18' are trimmed to accommodate tubularextension 42 of connector dielectric 36. The compensation of thedielectric value is effected by providing an air gap 72 of sufficientthickness by undercutting the inner side of an extended portion ofcollet 44' at 74. Since air has a lower dielectric value then foamedpolyolefin (or other dielectric used in cables), the thickness of theair gap can be selected to compensate for the higher dielectric value ofthe TFE and provide in combination with the thicknesses of thepolyolefin and the TFE an effective dielectric value, which closelyapproximates that of the thickness of the polyolefin in the cable. Theremaining components of the connector of FIG. 2 are similar in structureand function to corresponding components of the connector of FIG. 1.

It has been found that the assembly of connectors onto cables in thefield is facilitated by minimizing the number of components with whichthe workman must contend. This is accommodated by providing asubassembly of spacer 60, seal 62, washer 64 and backshell 52, which isshown in 1 16. 3. The interior parts are captivated within backshell 52by some suitable means such as stakes 76 which may be formed by use of apunch and hammer. The outer diameter of spacer 60 is relieved at 78 toprovide clearance for the stakes.

It will be appreciated from the foregoing that the inner radial,dimensions of backshell end 66, washer 64, seal 62, spacer 60 and colletclamp 46 would be made sufficiently large as to admit the largest cableof the group of cables to which the connector is applied and, in thecase of the spacer, to provide space within which excess seal materialwould be accommodated. It will also be appreciated that the onlycomponent that would not be interchangeable among particular cables ofthe group is collet 44. The inner surface of the collet would bespecially formed to sufficiently conform to or to provide adequategripping of the outer surface of the outer conductor of a particularcable, or sub-group of the group of cables, as to obtain the requiredmechanical strength and electrical continuity in the union.

While the foregoing describes the fundamental novel features of theinvention as applied to preferred embodiments, it will be understoodthat various omissions, substitutions and/or changes may be made bythose skilled in the art within the principle and scope of the inventionas expressed in the appended claims.

What I claim is:

1. in a connector for coaxial. cables of the RF type,

a combination which permits one connector to be suitable for use on agroup of cables having the same impedance characteristics and similarnominal size but different structural details while reducing the numberof loose components thereof in order to facilitate its connection onto acable, said combination comprising a. a body having an inner conductorand outer conductor and dielectric therebetween arranged at its forwardend for connection with another connector and at its rear end forreceiving any one of said group of cables, the outer conductor and someof the dielectric of said cable being removed from a forward portionthereof and said dielectric of said body extending rearwardly over saidexposed dielectric of said cable to provide a voltage standoff, andscrew threads on the rear end of said outer conductor for connection toa backshell,

a collet and collet clamp pair positioned at the rear end of said bodyfor applying clamping force upon the outer conductor of said cable inthe radially inward direction, only, upon axially forward movement ofsaid collet clamp relative to said collet, a forward portion of saidcollet extending over said tubular extension of the dielectric of thebody being dimensioned to provide an annular space between said portionof the collet and said extension of the dielectric to provide adjustmentof the dielectric value of the space between the outer surface of theinner conductor and the inner surface of said portion of said collet,and

. a subassembly including a backshell having screw threads at itsforward end for connection with said body and a radially inwardlyextending portion at its rear end, a deformable seal, a longitudinallyextending spacer positioned forward of said seal and means forcaptivating said seal and said spacer within said backshell, thedimensions of the captivated members and backshell being such that uponthe connection of said backshell to said body, said spacer is forcedagainst said seal thereby deforming said seal against said cable to makesealing contact

1. In a connector for coaxial cables of the RF type, a combination whichpermits one connector to be suitable for use on a group of cables havingthe same impedance characteristics and similar nominal size butdifferent structural details while reducing the number of loosecomponents thereof in order to facilitate its connection onto a cable,said combination comprising: a. a body having an inner conductor andouter conductor and dielectric therebetween arranged at its forward endfor connection with another connector and at its rear end for receivingany one of said group of cables, the outer conductor and some of thedielectric of said cable being removed from a forward portion thereofand said dielectric of said body extending rearwardly over said exposeddielectric of said cable to provide a voltage standoff, and screwthreads on the rear end of said outer conductor for connection to abackshell, b. a collet and collet clamp pair positioned at the rear endof said body for applying clamping force upon the outer conductor ofsaid cable in the radially inward direction, only, upon axially forwardmovement of said collet clamp relative to said collet, a forward portionof said collet extending over said tubular extension of the dielectricof the body being dimensioned to provide an annular space between saidportion of the collet and said extension of the dielectric to provideadjustment of the dielectric value of the space between the outersurface of the inner conductor and the inner surface of said portion ofsaid collet, and c. a subassembly including a backshell having screwthreads at its forward end for connection with said body and a radiallyinwardly extending portion at its rear end, a deformable seal, alongitudinally extending spacer positioned forward of said seal andmeans for captivating said seal and said spacer within said backshell,the dimensions of the captivated members and backshell being such thatupon the connection of said backshell to said body, said spacer isforced against said seal thereby deforming said seal against said cableto make sealing contact with said cable.